This invention relates to a linear motor of which its mover and its stator have magnetic teeth and is arranged such that the mover can move linearly on the stator while maintaining a constant gap with respect to the stator.
The main elements which contribute to the generation of driving force of this motor are: in the stator, many tooth-shaped bits of magnetic material (hereinafter called magnetic teeth) which are arranged along the longitudinal direction of the stator with a constant pitch, and in the mover, one or more permanent magnets, coils which are wound over cores sandwiching those permanent magnets, and groups of magnetic teeth formed on those cores. As mentioned above, this motor has magnetic teeth on the stator and on the mover, a permanent magnet, and an electromagnet, so that it is a "Hybrid Type" of motor as it is called. More particularly, motors whose stators have only magnetic teeth and whose movers have permanent magnets and the electromagnets with magnetic teeth, are known as examples of "SAWYER TYPE" linear stepping motors.
FIGS. 1a-1c show the principle of these known linear motors, and especially FIG. 1a shows the most fundamental example. A stator 1 is shown as having many magnetic teeth 2 which are arranged along the stator with a constant pitch. A mover 3 is shown as consisting of a permanent magnet 4, four groups of magnetic teeth 5, 6, 7, 8, cores 9, 9, and four separate four phase coils 10, 11, 12, 13 wound around cores 9, 9. However, each phase of the four groups of magnetic teeth 5, 6, 7, and 8 is different by 90 degrees from the other phases. FIG. 1b shows a more concrete example of FIG. 1a and in this figure, the mover is made smaller by replacing the four phase coils by two phase coils. Two phase coils 14 and 15 are shown in FIG. 1b. FIG. 1c shows the three phase model of the motor shown in FIG. 1a. In this example, three groups of magnetic teeth 16, 17, and 18 of the mover are shown and the phase of each tooth group is different by 120 degrees from the other phases. Three phase coils 19, 20 and 21 are also shown. In the above-noted conventional examples shown in FIG. 1a, 1b and 1c, it is normal for the mover 3 to progress in the longitudinal direction of the stator 1 by activating each coil in turn. The explanation of the fundamental principles of these motors is known to those skilled in the art, and is therefore omitted.